Hello,
I'm a beginner at modeling with Vensim and my question is about a fundamental concept. Attached you can find two images from Vensim help regarding the rework and errors. I have problem with workflow equation and do not know according to what equation my workflow graph can have the peaks after reaching zero. Your suggestion is highly appreciated.
Workflow equation in system with rework
Workflow equation in system with rework
- Attachments
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- 2.jpg (35.06 KiB) Viewed 2988 times
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- 1.jpg (33.63 KiB) Viewed 2988 times
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Re: Workflow equation in system with rework
I don't understand what you are asking. Can you upload your model and try and explain what you need?
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Re: Workflow equation in system with rework
please find attached the rework model, and its outcome graphs. I tried to repeat the rework model sample which is in the vensim help, and then compare the outcome of my model with the rework sample. However, as you can see, graphs of my model (work flow and work remaining graph is not the same as vensim sample). I think that my equation for work flow rate is not correct. Could you please let me know how I can fix it?
- Attachments
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- this work flow graph is not the same as the sample
- work flow graph.jpg (61.22 KiB) Viewed 2973 times
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- rework model1.mdl
- (3.07 KiB) Downloaded 159 times
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- the value of work remaining is negative after month 9, which shouldn't be correct
- equations&outputs.jpg (116.92 KiB) Viewed 2973 times
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Re: Workflow equation in system with rework
Is your equation different to the one in the Vensim sample model? You need to go through your work and check everything is identical to the Vensim model.ali wrote:Could you please let me know how I can fix it?
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Re: Workflow equation in system with rework
the vensim sample doesn't mention the "work flow" equation. so, I'm not sure my equation is correct or not, could you please let me know the correct equation for "work flow" variable in the vensim sample?
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Re: Workflow equation in system with rework
The model can be downloaded from
http://www.vensim.com/documentation/ind ... ?21495.htm
You will also find it on your hard drive under C:\Users\Public\Vensim\Help\Models\ModelGuide\3PROJ
http://www.vensim.com/documentation/ind ... ?21495.htm
You will also find it on your hard drive under C:\Users\Public\Vensim\Help\Models\ModelGuide\3PROJ
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Re: Workflow equation in system with rework
I haven't looked at it for a while, but the model in the Help system contains what I consider to be a fairly basic error, which is also in your sample above.
The workflow equation is not constrained such that the workflow is less than or equal to the available work, so Work Remaining goes negative.
In the final Help system model, it's:
and your equation is:
In both cases, this should be amended to something like:
The MIN( ... , Work Remaining/TIME STEP) ensures that Work Remaining remains nonnegative.
The workflow equation is not constrained such that the workflow is less than or equal to the available work, so Work Remaining goes negative.
In the final Help system model, it's:
Code: Select all
work flow = IF THEN ELSE(project is done,0,Veteran Workforce*productivity)
Code: Select all
work flow = 150*IF THEN ELSE(work remaining>0,1,0)
Code: Select all
work flow = IF THEN ELSE(project is done,0,MIN(Veteran Workforce*productivity,Work Remaining/TIME STEP))
/*
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*/
Advice to posters (it really helps us to help you)
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*/